1. Field of the Invention
The invention relates to an apparatus and a process for treating chlorosilane-containing liquids.
2. Description of the Related Art
Some processes and apparatuses of this type, in particular scrubber systems, are already known in the prior art.
U.S. Pat. No. 6,030,591 A discloses a process for removing and recovering halogenated hydrocarbons from process output streams. The term halogenated hydrocarbons encompasses perfluorinated hydrocarbons, partially fluorinated hydrocarbons and chlorofluorocarbons and also sulfur hexafluoride and nitrogen trifluoride. The removal of other gas components from fluorine compound gas streams is effected by oxidation combined with contact with a dry material (adsorption medium) or scrubbing medium.
In one embodiment, the use of an alkaline scrubbing medium (pH>9) for more efficient scrubbing of acidic gases is described. In addition, this alkali scrubber operates at above atmospheric pressure.
U.S. Pat. No. 4,519,999 A discloses a wastewater treatment in silicon production. It provides a combustion process with scrubbing of a liquid/a gas in a hydrolysis-neutralization zone by contact with water and an alkali metal present therein. The scrubber serves mainly to recover the hydrochloric acid formed by combustion of waste streams at various temperatures.
U.S. Pat. No. 5,246,682 A discloses a process for the wastewater-free work-up of residues from a chlorosilane distillation using hydrochloric acid. The process is carried out using hydrochloric acid with liberation of hydrogen chloride. Part of the reaction mixture coagulates and is removed by drying and heat treatment (˜140° C.).
U.S. Pat. No. 5,660,615 A discloses an offgas scrubbing process which comprises two steps. Firstly, a scrubbing stage is carried out in the temperature range 30-150° C. In a second step, the offgas is brought into contact with circulated aqueous salt solution having a pH of <5.
US 20040213721 A1 discloses an apparatus and a process for treating offgas streams at the place of use. The scrubbing process is based on an aqueous scrubbing medium containing a reducing agent (sodium thiosulfate, ammonium hydroxide, potassium iodide) and consists of at least two stages. In the scrubbing system, it is possible to use removable push-in beds composed of a plurality of packing materials.
U.S. Pat. No. 7,611,684 B2 and U.S. Pat. No. 5,757,660 A and also U.S. Pat. No. 5,246,594 A disclose scrubber control systems and processes. They are based on measurement methods for regulating and monitoring the pH and the concentration of the scrubbing medium. This is effected by means of a pH sensor, conductivity measurements or redox potential measurements.
U.S. Pat. No. 7,204,963 B2 also discloses a process consisting of two steps for separating chlorosilanes from gas streams. The offgas stream is, in a first stage treated with steam in the gas phase and then, in a second stage, treated with a liquid, aqueous phase.
US 20110150739 A1 discloses a process for removing boron-containing impurities from halosilanes and an apparatus for carrying out the process.
U.S. Pat. No. 4,408,030 A discloses a waste chlorosilane treatment using an aqueous medium. The scrubbing medium contains concentrated hydrochloric acid.
JP 2157020 A discloses a process for treating dichlorosilane-containing gas with alkaline earth metal hydroxides or oxides having a pH of 6-8.5.
The prior art does not disclose any processes in which chlorosilanes can be removed in a single step and under ambient conditions without having to make recourse to packing materials. In addition, waste streams containing particles are often obtained in the prior art.
The objective of the invention arose from these problems.